Specification 9 Cavity barriers for fire-protected timber
2019: Spec C1.13: 1
Specification 9 sets out requirements for cavity barriers used for fire-protected timber. A cavity barrier is a barrier/enclosure provided to cavities within, around or adjacent to fire-protected timber. The purpose of a cavity barrier is to limit the spread of fire, smoke and hot gases to other parts of a building in the event of a fire. A cavity barrier is used under C2D13 to permit fire-protected timber to be used in lieu of non-combustible material.
The requirements for cavity barriers in Specification 9 include but are not limited to:
- the location of cavity barriers, i.e. junctions between fire-resisting floor/ceiling assemblies and fire-resisting walls;
- minimum thickness of timber used as a barrier;
- minimum thickness of insulation; and
- the method to determine the FRL of the cavity barrier.
2019: Spec C1.13: 2
- At concealed cavities adjacent to junctions between fire-resisting floor/ceiling assemblies and fire-resisting walls.
- At concealed cavities adjacent to junctions between fire-resisting floor/ceiling assemblies and fire-resisting or non-combustible external walls.
- At concealed cavities adjacent to junctions between fire-resisting walls and fire-resisting or non-combustible external walls.
- Around the perimeter of door and window openings in fire-resisting construction.
- Horizontal cavity barriers — at not more than 5 m centres.
- Vertical cavity barriers — at not more than 10 m centres.
- achieve the performance specified in Table S9C2 based on the highest FRL of the elements they are mounted within or seal against; or
- consist of—
- the frame is constructed of steel or timber with the minimum thickness specified in Table S9C2 for timber; and
- the frame is tightly fitted to rigid construction and mechanically fixed in position.
|System required FRL
|–/60/60 or –/90/90
|–/120/120, –/180/180 or –/240/240
|Cavity barrier required FRL
|Timber, required minimum thickness
|Mineral wool, required minimum thickness
Minimum thicknesses are to be measured in the direction of heat flow.